1. Field of the Invention
This invention concerns a novel 4-substituted-1,2,3,6-tetrahydrophthalic acid anhydride represented by the structural formula [I]: ##STR2## where R.sup.1 represents a lower alkoxy group, and R.sup.2 l and R.sup.3 each represents a lower alkyl group or a lower alkoxy group, said 4-substituted-1,2,3,6-tetrahydrophthalic acid anhydride being liquid.
2. Description of the Prior Art
Heretofore, 2-(triethyl)-silyl-1,3-butadiene is described in Tetrahedron Letters as a derivative of an organic silicon compound having a butadienyl group, and preparation of 4-(triethyl)-siyl-1,2,3,6-tetrahydrophthalic acid anhydride therefrom through the reaction with maleic acid anhydride is also described (Tetrahedron Letters, 36, 3323, 1978).
As to such organic silicon compounds the present inventor has found that novel silicon compounds having the butadiene group, that is, 2-substituted-1,3-butadiene compounds, for example, 2-(trimethoxy)silyl-1,3-butadiene, 2-(methoxydimethyl)- silyl-1,3-butadiene, and 2-(dimethoxymethyl)silyl-1,3- butadiene are effective as plasticizers for vinyl chloride resins or the like, silane coupling agents, etc. and have already proposed such novel compounds and the process for producing them (refer to Japanese Patent Application No. 33733/1984 or U.S. patent application Ser. No. 704088).